Chemical mechanical polishing compositions for copper and associated materials and method of using same

ABSTRACT

A CMP composition containing a rheology agent, e.g., in combination with oxidizing agent, chelating agent, inhibiting agent, abrasive and solvent. Such CMP composition advantageously increases the materials selectivity in the CMP process and is useful for polishing surfaces of copper elements on semiconductor substrates, without the occurrence of dishing or other adverse planarization deficiencies in the polished copper.

FIELD OF THE INVENTION

The present invention relates to a chemical mechanical polishingcomposition and to a method of using same for the polishing ofsemiconductor substrates having copper thereon, e.g., copperinterconnects, electrodes, or metallization, as part of a semiconductordevice structure on a wafer substrate.

DESCRIPTION OF THE RELATED ART

Copper is employed in semiconductor manufacturing as a material ofconstruction for components of semiconductor device structures on wafersubstrates (e.g., contacts, electrodes, conductive vias, field emitterbase layers, etc.), and it is rapidly becoming the interconnect metal ofchoice in semiconductor manufacturing due to its higher conductivity andincreased electromigration resistance relative to aluminum and aluminumalloys.

Typically, the process scheme for utilizing copper in semiconductormanufacturing involves the damascene approach, wherein features areetched in a dielectric material. In the dual damascene process a singlefill is used to form both plugs and lines. Since copper has a propensityto diffuse into the dielectric material, leading to leakage betweenmetal lines, barrier/liner layers, such as Ta or TaN deposited byvarious deposition methods, are often used to seal the copperinterconnects. Following deposition of the liner layer material, a thinseed layer of copper is deposited on the liner material via physical orchemical vapor deposition, followed by electrodeposition of copper tofill the features.

As copper is deposited to fill the etched features, elevationaldisparity or topography develops across the surface of the layer, havingraised and recessed regions. The deposited copper overburden must thenbe removed to render it of suitable form to accommodate subsequentprocess steps in the fabrication of the finished semiconductor product,and in order to satisfactorily operate in the micro-circuitry in whichit is present. The planarization typically involves chemical mechanicalpolishing (CMP), using a CMP composition formulated for such purpose.

Chemical Mechanical Polishing or Planarization (“CMP”) is a process inwhich material is removed from a surface of a semiconductor wafer, andthe surface is polished (planarized) by coupling a physical process suchas abrasion with a chemical process such as oxidation or chelation. Inits most rudimentary form, CMP involves applying slurry, a solution ofan abrasive and an active chemistry, to a wafer surface or polishing padthat buffs the surface of the semiconductor wafer to achieve theremoval, planarization, and polishing process.

Due to the difference in chemical reactivity between copper and theliner layer, e.g. Ta or TaN, two chemically distinct slurries are oftenused in the copper CMP process. The first step slurry (Step I) istypically used to rapidly planarize the topography and to uniformlyremove the remaining copper, with the polish stopping at the linerlayer. The second step slurry (Step II) typically removes the liner(barrier) layer material at a high removal rate and stops on thedielectric layer, or alternatively on a cap layer that has been appliedto protect the dielectric. Typical Step 1 slurries have a high copperremoval rate, and a copper to liner material removal rate selectivity ofgreater than 4:1.

At the point at which copper is removed to expose the underlying linermaterial between features the slurry requirements rapidly change.However, until the copper layer is removed between features, as would beindicated by an endpoint detection system, the copper polishingcontinues until all copper overburden is removed between featurepatterns. The period of time from liner exposure to the end of thepolishing step is referred to as over-polish, during which time, dishinginto copper features occurs and wafer surface planarity is lost.

Dishing occurs when too much copper is removed such that the coppersurface is recessed relative to the liner and/or dielectric surface ofthe semiconductor wafer. Dishing occurs when the copper and linermaterial removal rates are disparate. Oxide erosion occurs when too muchdielectric material is removed. Dishing and oxide erosion are dependenton area, pattern and pitch.

Using a polishing formulation having the appropriate selectivity for thematerial(s) to be removed is one key to obtaining uniform planarizationacross the wafer surface. Uniform distribution of abrasive and padmechanical force are further keys to obtaining good planarity.

Of concern to commercial CMP slurries is that the abrasive materials inthe slurries produce defects in the form of micro-scratches. Anotherconcern is poor planarization efficiency, which is the ability of theslurry to polish high points preferentially over low points on thesurface of the wafer. Micro-scratches and poor planarization efficiencyresult in integrated circuits with increased defects and a lower yield.

An object of this invention, therefore, is a CMP formulation forplanarization of a wafer surface having copper deposited thereon, theformulation having a high copper removal rate, a comparatively low linermaterial removal rate, appropriate material selectivity ranges tominimize copper dishing at the onset of liner exposure, and goodplanarization efficiency.

SUMMARY OF THE INVENTION

The present invention relates to CMP compositions containing a rheologyagent and to copper CMP using such compositions.

In one aspect, the invention relates to a CMP composition forplanarization of copper containing films, in which the compositionincludes at least an abrasive and a rheology agent.

In a further aspect, the invention relates to a CMP composition forplanarization of copper films, in which the composition includes atleast an abrasive component, an oxidizing agent, and a rheology agent.

In a still further aspect, the present invention relates to a CMPformulation for use in the planarization of a copper containing wafersurface, wherein said formulation comprises first “1a” and second “1b”slurry compositions, said “1a” composition comprising:

oxidizing agent 0.1 to 30 wt. % passivating agent 0.01 to 10 wt. %chelating agent 0.1 to 25 wt. % and rheology agent 0.0 to 65 wt. % andabrasive 0.0 to 30 wt. %and said “1b” composition comprising:

oxidizing agent 0.01 to 30 wt. % passivating agent 0.01 to 10 wt. %chelating agent 0.1 to 25 wt. % rheology agent 0.001 to 65 wt. % andabrasive 0.0 to 30 wt. %.

Still another aspect of the invention relates to a method of polishingcopper on a substrate having copper thereon, including contacting copperon the substrate under CMP conditions with a CMP composition effectivefor polishing the copper, wherein the CMP composition includes arheology agent.

Other aspects, features and embodiments of the invention will be morefully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a depiction of laminar flow consistent with the meaning ofthe term as used herein.

FIGS. 2 a and 2 b illustrate one affect of a rheology agent on laminarflow in a CMP process according to one embodiment of the presentinvention.

FIGS. 3 a through 3 c show a comparison of a step 1(a&b) CMP process(circles) relative to a step 1(a) only process according to oneembodiment of the present invention.

FIG. 4 shows electrical resistance data for 100 μm lines for differentoverpolishing times employing a step 1(a&b) slurry process.

DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS THEREOF

The present invention is based on the discovery that a rheology agent ina CMP slurry modifies the slurry's fluid dynamics, by reducing thefluid's vertical flow. Vertical flow is defined as the flow componentperpendicular to the primary flow plane or wafer surface. The rheologyagent improves the material selectivity of the CMP process whilemaintaining a high level of copper planarization and good uniformity.

In CMP slurries it is advantageous to independently control the relativepolishing rates between the different materials of the pattern to bepolished. For example, in copper polishing one will actually polishcopper, liner or barrier materials such as tantalum and tantalum nitrideas well as dielectrics such as SiO₂, SiN, FSG, capping layers and low-kdielectrics.

The present invention relates to a CMP composition for use inplanarizing copper containing semiconductor wafer surfaces, and to CMPprocesses using such composition. The composition includes a rheologyagent, which serves to increase selectivity between copper and linerwithout affecting the copper removal rate.

The present invention, in its broadest sense relates to a CMPcomposition for planarization of copper films, the CMP compositioncomprising at least an abrasive and a rheology agent.

Rheology¹ is the study of the change in form and flow of matter, andembraces elasticity, viscosity and plasticity. Viscosity is a measure ofinternal friction in a fluid, caused by intermolecular attraction, whichmakes the fluid resist a tendency to flow. ¹More Solutions to StickyProblems, Brookfield Engineering Labs, Inc., P. 13

Addition of a rheology agent to a CMP slurry composition provides ameans by which to modify the slurry's viscosity and laminar fluid flow,which encompasses the movement of one layer of the slurry past another,with a reduced transfer of matter between layers.

FIG. 1 shows a depiction of laminar flow consistent with the meaning ofthe term as used herein. When a fluid 14, such as a CMP slurry is boundby two opposing plates, whereby one plate 10, moves while the secondplate 12, remains stationary, it is found that there is a layer orlamina of fluid (slurry) 16, which moves with the plate, and a layerclosest to the stationary plate which remains essentially stationary 18.The fluid or slurry tends to move in layers with each layer having asuccessively higher speed that creates a gradient of velocity as youmove from the stationary to the moving plate. The gradient of velocity,also referred to as shear rate or rate of strain, is defined as thevelocity of top layer 16, with respect to the thickness of the film 20.

Rheology agents in CMP slurries can be used to control dishing anderosion phenomena during planarization of sub-micron features.

A pseudoplastic rheology agent introduces a flow behavior in which theviscosity of the slurry decreases as shear rate increases. During a CMPprocess shear rate is highest at elevated topography (protuberances andasperities), allowing for greater material removal through increasedabrasive particle momentum and mechanical polishing. And, reactants areprovided more readily by means of higher fluid flow to the low viscosityareas near the asperities. In the vias and line trenches, where theshear rate is lower, a localized higher viscosity reduces fluidvelocities. Lower fluid velocities help to maintain the passivationlayer by reducing reactant transport and mechanical abrasion caused byturbulent mixing.

A rheology agent that increases the viscosity and laminar flowadvantageously decreases the vertical flow of the slurry. In terms ofpolishing, this causes abrasive particles to move almost exclusively inthe direction of the flow plane of the lamina between the wafer surfaceand the polishing pad.

FIGS. 2 a and 2 b illustrate one effect of a rheology agent on laminarflow in a CMP process. In FIG. 2 a, slurry-abrasive particles 20, flowfreely in a three dimensional space between wafer 22, which includescopper features 24 and liner material 26, and polishing pad 28. FIG. 2 bshows the CMP process as in FIG. 2 a, modified by addition of a rheologyagent to the CMP slurry. Abrasive particles 20, become constrained inthe flow plane (laminas) between wafer 22 and pad 26, thereby reducingwear to the copper features, by improving selectivity between copper 24,and liner 26, without reducing the overall copper removal rate.

Preferably, the rheology agent used in the CMP composition of thepresent invention is compatible and stable when combined with othercomponents in a slurry. Moreover, the rheology agent should be stable ina particular pH range and with a particular oxidizer. Preferred Rheologyagents are soluble in the active slurry components and non-reactive withthe wafer surface chemistry.

Useful rheology agents include but are not limited to cross-linkedacrylic polymers and Water Soluble Polymers (WSPs). More particularly,useful rheology agents include Noveon's Carbopol® series of polymers(Cleveland Ohio), modified cellulose derivatives, cellulose ethers,starch derivatives, pectin derivatives, polyacylamides; and aqueousdispersions thereof. In a preferred embodiment, the rheology agent mostuseful in the present invention is selected from the group consisting ofhydroxypropylcellulose, hydroxyethylcellulose, both availablecommercially from Aqualon (Wilmington, Del.) and carboxymethylcellulose.

In slurry, the rheology agent increases the viscosity, and structuresits laminar flow such that vertical fluid motion is reduced. In apreferred embodiment, the rheology agent used in the present inventionis hydroxypropylcellulose having a molecular weight of in the range of300,000 to 1,000,000 MW.

Rheology agents tend to be polymeric and therefore molecular weightrequirements differ depending on the type of rheology agent. For a classof water soluble polymers molecular weights greater than 50,000 arepreferred.

In one embodiment, the present invention relates to a CMP compositionfor use in planarizing a wafer surface, said composition comprising atleast an abrasive, and a rheology agent, such that the rheology agentincreases the viscosity and laminar flow of the CMP composition.Preferably, the rheology agent increases the viscosity of the CMPcomposition to between 1.5 cSt and 50 cST at 25° C. and more preferablyto a range that is between 3.0 to 5.0 cSt.

In a further embodiment, the present invention relates to an aqueous CMPcomposition for planarization of a wafer surface having a copper layerdeposited thereon, the copper layer having been deposited during acopper damascene processing step, wherein said composition comprises anabrasive component, an oxidizing agent, and a rheology agent having thefollowing concentrations by weight based on the total weight of thecomposition:

from about 0 to 30 wt. % abrasive;

from about 0.01 to 30 wt. % oxidizing agent; and

from about 0.001 to 60 wt. % rheology agent.

In a still further embodiment, the present invention relates to anaqueous CMP composition for planarization of a wafer surface having acopper layer deposited thereon, the copper layer having been depositedduring a copper damascene processing step, wherein said compositioncomprises an abrasive, oxidizing agent, chelating agent, inhibitingagent, and rheology agent having the following concentrations by weightbased on the total weight of the composition:

from about 0 to 30 wt. % abrasive;

from about 0.01 to 30 wt. % oxidizing agent;

from about 0.1 to 25 wt. % chelating agent;

from about 0.001 to 10 wt. % rheology agent.

The abrasive component as used herein may be of any suitable type,including, without limitation, oxides, metal oxides, silicon nitrides,carbides, etc. Specific examples include silica, alumina, siliconcarbide, silicon nitride, iron oxide, ceria, zirconium oxide, tin oxide,titanium dioxide, and mixtures of two or more of such components insuitable form, such as grains, granules, particles, or other dividedform. Alternatively, the abrasive can include composite particles formedof two or more materials, e.g., NYACOL® alumina-coated colloidal silica(Nyacol Nano Technologies, Inc., Ashland, Mass.). Alumina is a preferredinorganic abrasive and can be employed in the form of boehmite ortransitional δ, θ or γ phase alumina. Organic polymer particles, e.g.,including thermoset and/or thermoplastic resin(s), can be utilized asabrasives. Useful resins in the broad practice of the present inventioninclude epoxies, urethanes, polyesters, polyamides, polycarbonates,polyolefins, polyvinylchloride, polystyrenes, polyolefins, and(meth)acrylics. Mixtures of two or more organic polymer particles can beused as the abrasive medium, as well as particles comprising bothinorganic and organic components. In a preferred embodiment, theabrasive component of the present invention includes alumina-coatedcolloidal silica.

The term oxidizing agent as used herein is defined as any substancewhich removes metal electrons and raises the atomic valence and includesbut is not limited to hydrogen peroxide (H₂O₂), ferric nitrate(Fe(NO₃)₃), potassium iodate (KIO₃), potassium permanganate (KMnO₄),nitric acid (HNO₃), ammonium chlorite (NH₄ClO₂), ammonium chlorate(NH₄ClO₃), ammonium iodate (NH₄BO₃), ammonium perborate (NH₄BO₃),ammonium perchlorate (NH₄ClO₄), ammonium periodate (NH₄BO₃), ammoniumpersulfate ((NH₄)₂₅₂O₈), tetramethylammonium chlorite ((N(CH₃)₄)ClO₂),tetramethylammonium chlorate ((N(CH₃)₄)ClO₃), tetramethylammonium iodate((N(CH₃)₄)IO₃), tetramethylammonium perborate ((N(CH₃)₄)BO₃),tetramethylammonium perchlorate ((N(CH₃)₄)ClO₄), tetramethylammoniumperiodate ((N(CH₃)₄)IO₄), tetramethylammonium persulfate((N(CH₃)₄)S₂O₈), urea hydrogen peroxide ((CO(NH₂)₂)H₂O₂). The preferredoxidizing agent for the CMP slurry composition of the instant inventionis hydrogen peroxide.

Alternatively, the oxidizing agent may comprise an amine-N-oxide havingthe formula (R¹R²R³N→O), wherein R¹R²R³ are independently selected fromthe group consisting of: H and C₁-C₈ alkyl. Specific examples ofamine-N-oxides include but are not limited to 4-methylmorpholine N-oxide(C₅H₁₁NO₂) and pyridine-N-oxide (C₅H₅NO).

The term chelating agent as used in the present CMP composition isintended to mean any substance that in the presence of a watercontaining solution solubilizes or etches the oxidized copper material.Copper chelating agents useful in the present invention include but arenot limited to inorganic acids (i.e. phosphoric acid) and organic acids,amines and amino acids (i.e. glycine, alanine, citric acid, acetic acid,maleic acid, oxalic acid, malonic acid, succinic acid, nitrilotriaceticacid, iminodiacetic acid, ethylenediamine, and EDTA). A preferredchelating agent is glycine. 21.

The term corrosion inhibitor as used herein, is intended to mean anysubstance that reacts with the fresh copper surface and/or oxidizedcopper thin film to passivate the copper layer and prevent excessiveetching of the copper surface during CMP. Preferably, the CMPcomposition of the present invention has a static metal etch rate ofless than 500 Å/min, more preferably less than 200 Å/min, and mostpreferably less than 50 Å/min.

The corrosion inhibitor component in the CMP composition of theinvention may comprise one or more inhibitor components including forexample, imidazole, aminotetrazole, benzotriazole, benzimidazole, amino,imino, carboxy, mercapto, nitro, alkyl, urea and thiourea compounds andderivatives, etc. Dicarboxylic acids such as oxalic acid, malonic acid,succinic acid, nitrilotriacetic acid, iminodiacetic acid, andcombinations thereof are also useful corrosion inhibitors. Preferredinhibitors include tetrazoles and their derivatives. In a specificembodiment, the corrosion inhibitor is 5-aminotetrazole (ATA).

The pH of the present CMP compositions may be at any suitable value thatis efficacious for the specific polishing operation employed. In oneembodiment, the pH of the CMP composition can be in a range of fromabout 2 to about 11, more preferably in a range of from about 2 to about7.0, and most preferably in a range of from about 3 to about 6.

The solvents employed in the CMP compositions of the invention can besingle component solvents or multicomponent solvents, depending on thespecific application. In one embodiment of the invention, the solvent inthe CMP composition is water. In another embodiment, the solventcomprises an organic solvent, e.g., methanol, ethanol, propanol,butanol, ethylene glycol, propylene glycol, glycerin, etc. In yetanother embodiment, the solvent comprises a water-alcohol solution. Awide variety of solvent types and specific solvent media can be employedin the general practice of the invention to provide asolvating/suspending medium in which the abrasive is dispersed and inwhich the other components are incorporated to provide a composition ofappropriate character, e.g., of slurry form, for application to theplaten of the CMP unit to provide a desired level of polishing of thecopper on the wafer substrate.

Bases can be optionally employed for pH adjustment in compositions ofthe invention. Illustrative bases include, by way of example, potassiumhydroxide, ammonium hydroxide and tetramethylammonium hydroxide (TMAH),tetraethylammonium hydroxide, trimethyl hydroxyethylammonium hydroxide,methyl tri(hydroxyethyl) ammonium hydroxide, tetra(hydroxyethyl)ammoniumhydroxide, and benzyl trimethylammonium hydroxide.

Acids can also be optionally employed for pH adjustment and buffering inthe CMP compositions of the invention. The acids used can be of anysuitable type, including, by way of example, formic acid, acetic acid,propanoic acid, butanoic acid, pentanoic acid, isovaleric acid, hexanoicacid, heptanoic acid, octanoic acid, nonanoic acid, lactic acid,hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid,hydrofluoric acid, malic acid, fumaric acid, malonic acid, glutaricacid, glycolic acid, salicylic acid, 1,2,3-benzenetricarboxylic acid,tartaric acid, gluconic acid, citric acid, phthalic acid, pyrocatechoicacid, pyrogallol carboxylic acid, gallic acid, tannic acid, and mixturesincluding two or more acids of the foregoing or other types.

Amines when present can be of any suitable type, including, by way ofexample, hydroxylamine, monoethanolamine, diethanolamine,triethanolamine, diethyleneglycolamine, N-hydroxylethylpiperazine,N-methylethanolamine, N,N-dimethylethanolamine, N-ethylethanolamine,N,N-diethylethanolamine, propanolamine, N,N-dimethylpropanolamine,N-ethylpropanolamine, N,N-diethylpropanolamine,4-(2-hydroxyethyl)morpholine, aminoethylpiperazine, and mixturesincluding two or more of the foregoing or other amine species.

Surfactants when optionally employed in the CMP compositions of theinvention can be of any suitable type, including non-ionic, anionic,cationic, and amphoteric surfactants, and polyelectrolytes including,for example: salts of organic acids; alkane sulfates (e.g., sodiumdodecyl sulfate); alkane sulfonates; substituted amine salts (e.g.,cetylpyridium bromide); betaines; polyethylene oxide; polyvinyl alcohol;polyvinyl acetate; polyacrylic acid; polyvinyl pyrrolidone;polyethyleneimine; and esters of anhydrosorbitols, such as thosecommercially available under the trademarks Tween® and Span®, as well asmixtures including two or more of the foregoing or other surfactantspecies.

In one embodiment, the invention provides an aqueous-slurry, CMPcomposition useful for planarizing substrates having copper thereon,e.g., copper interconnects, metallization, device structural elements,etc., in which the composition includes H₂O₂, hydroxypropylcelluose,glycine, ATA, and abrasive, having the following composition ranges byweight, based on the total weight of the composition:

ATA 0.01 to 10 wt. % H₂O₂ 0.01 to 30 wt. % Glycine 0.1 to 25 wt. %Hydroxypropylcellulose (1,000,000 MW) 0.01 to 5 wt. % Alumina coatedsilica composite abrasive 0 to 30 wt. %

In a further specific illustrative embodiment, the CMP compositioncomprises the following components by weight, based on the total weightof the composition:

ATA 0.01-10 wt. % H₂O₂ 0.01-30 wt. % Glycine 0.1-25 wt. %Hydroxypropylcellulose (1,000,000 MW) 0.01 to 5 wt. % Abrasive 0-30 wt.% Water 30-90 wt. %with the total wt. % of all components in the composition totaling to100 wt. %.

Based on a study conducted by M. Hariharaputhiran, J. Zhang, S.Ramarajan, J. J. Keleher, Yuzhuo Li, and S. V. Babu, all of ClarksonUniversity¹, when both Cu²⁺ and glycine are present in a CMP solutioncomprising H₂O₂, the Cu²⁺ and glycine react to form a [Cu²⁺-(gly)₂]chelate, which catalyzes the dissociation reaction of H₂O₂ into OH⁻ and.OH. The .OH having a higher oxidation potential than H₂O₂, acceleratesthe rate of oxidation of the copper surface and hence the polish ratesof the copper substrate. At the point of liner exposure, copperavailability is reduced to the surface area of the feature, and as aconsequence, dishing into the copper features occurs and wafer surfaceplanarity is lost. ¹M. Hariharaputhiran, et al., “Hydroxyl RadicalFormation in H₂O₂-Amino Acid Mixtures and Chemical Mechanical Polishingof Copper”, Journal of The Electrochemical Society, 2000, 147(10)3820-3826

The present invention makes use of a rheology agent's functionality toimpart characteristics to a CMP formulation that result in lowering thedegree to which dishing occurs into copper features by modifying theformulation's viscosity and laminar fluid flow.

Accordingly, the present invention advantageously reduces the degree towhich dishing into copper features occurs at the onset of linerexposure, by decreasing the wear to such features caused by turbulenceand abrasive particles, while maintaining the mechanical copper removalrate.

As one alternative, the CMP formulation of the present invention may bemodified so as to vary the concentration of oxidizer in the slurrycomposition at or just prior to the onset of liner exposure. As the rateof copper removal is a function of oxidizing agent concentration,reducing the concentration thereof, affects the degree to which dishingoccurs at the time of liner exposure.

The reduction in oxidizing agent, may be accomplished, by switching ofCMP formulations during planarization or in the case where oxidizingagent (i.e. H₂O₂) is combined in situ on the CMP tool's platen, byreducing the amount of oxidizing agent delivered to the platen. Thelatter method eliminates the need for two separate slurries.

Accordingly, the present invention, in a further embodiment, relates toa CMP formulation for use in the planarization of a copper containingwafer surface, wherein said formulation comprises first and secondslurry compositions having varying material removal selectivities as aresult of varying the concentration of an oxidizing agent component inthe first and second compositions. Preferably the second composition isa chemical variant of the first whereby the removal selectivities ofcopper and liner materials are altered by reducing the concentration ofthe oxidizing agent component.

The first slurry composition, referred to as “1a”, having a highconcentration of oxidizing agent, removes bulk copper overburden at highremoval rates, without causing liner exposure. Preferably, the “1a”composition removes copper at a rate that is between about 2,000 Å/minand 6,000 Å/min and more preferably at a rate that is between about3,000 Å/min and 5,000 Å/min.

The second composition, referred to as “1b”, having a significantlyreduced oxidizing agent concentration as compared to composition “1a”,removes and planarizes the remaining copper overburden and exposes theliner layer. As a result of lowering the concentration of oxidizingagent, the “1b” composition removes copper at a rate lower than that offormulation “1a”. Preferably, the “1b” composition removes copper at arate that is between about 500 Å/min and 3,000 Å/min and more preferablyat a rate that is between about 1,000 Å/min and 2,000 Å/min.

In a further embodiment, the present invention relates to a “1b” slurrycomposition comprising a rheology agent and an oxidizing agent, whereinsaid oxidizing agent is present in a concentration that is less than a“1a” composition.

In a still further embodiment, the present invention relates to a CMPformulation for use in the planarization of a copper containing wafersurface, wherein said formulation comprises first “1a” and second “1b”slurry compositions, said “1a” composition comprising the followingcomposition ranges by weight, based on the total weight of thecomposition:

oxidizing agent 0.1 to 30 wt. % passivating agent 0.01 to 10 wt. %chelating agent 0.1 to 25 wt. % and abrasive 0 to 30 wt. %

and said “1b” composition comprising the following composition ranges byweight, based on the total weight of the composition:

oxidizing agent 0.01 to 30 wt. % passivating agent 0.01 to 10 wt. %chelating agent 0.1 to 25 wt. % Hydroxypropylcellulose (1,000,000 MW)0.01 to 5 wt. % and abrasive 0 to 30 wt. %.

In a more preferred embodiment, the present invention relates to a CMPformulation for use in the planarization of a copper containing wafersurface, wherein said formulation comprises first “1a” and second “1b”slurry compositions, said “1a” composition comprising the followingcomposition ranges by weight, based on the total weight of thecomposition:

ATA 0.01 to 10 wt. % H₂O₂ 0.1 to 30 wt. % Glycine 0.1 to 25 wt. %Hydroxypropylcellulose (1,000,000 MW) 0.01 to 5 wt. % and Alumina coatedsilica composite abrasive 0 to 30 wt. %and said second “1b” composition comprising the following compositionranges by weight, based on the total weight of the composition:

ATA 0.01 to 10 wt. % H₂O₂ 0.01 to 30 wt. % Glycine 0.1 to 25 wt. %Hydroxypropylcellulose (1,000,000 MW) 0.01 to 5 wt. % and Alumina coatedsilica composite abrasive 0 to 30 wt. %

The CMP compositions of the invention can be readily formulated in aso-called ‘day tank’ or ‘storage tank,’ or the CMP composition can beprovided as a two-part formulation or a multi-part formulation that ismixed at the point of use. The advantage of a multi-part formulationresides in its extended shelf life, relative to single-packageformulations. A single package formulation is more susceptible todecomposition and change of its properties over time, in relation to amulti-part formulation, due to the presence of the oxidizer in thesingle-package CMP composition. The individual parts of the multi-partformulation can be mixed at the polishing table, polishing belt or thelike, or in an appropriate container shortly before reaching thepolishing table.

In one embodiment, each single ingredient of the CMP composition isindividually delivered to the polishing table for combination at thetable with the other ingredients of the formulation, to constitute theCMP composition for use. In another embodiment, the CMP composition isformulated as a two-part composition in which the first part comprisesabrasive, corrosion inhibitor and rheology agent in aqueous medium, andthe second part comprises oxidizing agent and chelating agent. In stillanother embodiment, the CMP composition is formulated as a two-partcomposition in which the first part comprises all components of thecomposition except the oxidizer, and the second part comprises theoxidizer. In all of these various embodiments, the mixing of ingredientsor parts to form the final composition occurs at the point of use, withmixing at the polishing table, polishing belt or the like, or in anappropriate container shortly before reaching the polishing table.

The copper CMP composition of the invention can be utilized in aconventional manner in the CMP operation, by application of the CMPcomposition to the copper surface on the wafer substrate in aconventional fashion, and polishing of the copper surface can be carriedout using a conventional polishing element such as a polishing pad,polishing belt, or the like.

The CMP composition of the invention is advantageously employed topolish surfaces of copper elements on semiconductor substrates, withoutthe occurrence of dishing or liner or dielectric erosion.

CMP slurry compositions of the invention are highly effective forpolishing copper on semiconductor wafer substrates, e.g., polishing ofpatterned copper wafers. The CMP compositions of the invention can bereadily prepared by mixing of ingredients in the desired single-packageor multi-part formulations, consistent with the foregoing discussionherein of single-package and multi-part formulations. The concentrationsof the respective ingredients can be widely varied in specificformulations of the CMP composition, in the practice of the invention,and it will be appreciated that the CMP composition of the invention canvariously and alternatively comprise, consist or consist essentially ofany combination of ingredients consistent with the disclosure herein.

The features and advantages of the invention are more fully shown by theempirical examples and results discussed below.

EXAMPLES Example 1

In one experiment 0.1% hydroxypropylcellulose with 1,000,000 MW wascombined with:

4% glycine;

0.8% amino-tetrazole;

5% hydrogen peroxide; and

1% Nyacol DP6243 alumina coated silica composite abrasive.

The copper polish rate remained the same as without the addition of therheology agent at approximately 4000 Å/min. However, tantalum (liner)polishing rate decreased from 40 Å/min to 30 Å/min, increasingselectivity from 100:1 to 133:1.

Example 2

In a second experiment, the copper line dishing was compared between aone step copper polish using only the composition shown below under Step1(a) and a two step (a&b) copper polish using the composition shownbelow under Step 1(a) and Step 1(b).

Step 1 (a) formulation

4% glycine;

0.8% amino-tetrazole;

5% hydrogen peroxide; and

1% alumina coated silica composite abrasive.

Step 1 (b) formulation

4% glycine;

0.8% amino-tetrazole;

0.4% hydrogen peroxide;

1% alumina coated silica composite abrasive.

0.1% hydroxypropylcellulose with 1,000,000 MW;

FIGS. 3 a through 3 c compare dishing data of a Step 1(a&b) CMP process(circles) relative to a Step 1(a) only process (squares) for differentline widths (isolated lines). A decrease in the concentration of theoxidizing agent prior to liner exposure reduces dishing effects by morethan 500 Å (see 1.5 μm line width). The data is taken for different dieon the wafer. FIGS. 3 a, 3 b and 3 c show dishing in the center die,donut (half radius) die and edge die, respectively.

Example 3

FIG. 4 shows electrical resistivity data for different overpolishingtimes for 100 μm lines. As the overpolishing time increases, so too doesline dishing, which results in a decreasing of the cross section of theline. A decrease in the area of the cross section increases theelectrical resistivity of the line. The relative increase in the lineresistivity stays small in comparison to the line resistivity even forlong overpolishing times. Thus a robust process is achieved by utilizingthe described step 1a and 1b slurry to remove the Cu overburden andplanarize the wafer surface.

While the invention has been described herein in reference to specificaspects, features and illustrative embodiments of the invention, it willbe appreciated that the utility of the invention is not thus limited,but rather extends to and encompasses numerous other variations,modifications and alternative embodiments, as will suggest themselves tothose of ordinary skill in the field of the present invention, based onthe disclosure herein. Correspondingly, the invention as hereinafterclaimed is intended to be broadly construed and interpreted, asincluding all such variations, modifications and alternativeembodiments, within its spirit and scope.

1.-39. (canceled)
 40. A method of planarizing a wafer substrate havingcopper films deposited thereon, said method comprising contacting copperwith a composition to remove the copper and expose an underlying linerlayer, said composition comprising the following composition ranges byweight, based on the total weight of the composition: oxidizing agent0.01 to less than 30 wt. % passivating agent 0.01 to 10 wt. % chelatingagent 0.1 to 25 wt. % and abrasive 0 to 30 wt. %, rheology agent 0.01 to5 wt. %

wherein the rheology agent is effective at maintaining the desiredviscosity and/or shear rate of the composition while in contact with thesubstrate.
 41. The method of claim 40, wherein the composition hasviscosity between 1.5 cSt and 50 cSt at 25° C.
 42. The method of claim40, wherein viscosity decreases as shear rate increases.
 43. The methodof claim 40, wherein said rheology agent is selected from the groupconsisting of: Water Soluble Polymers (WSPs) and cross-linked acrylicacid based polymers.
 44. The method of claim 40, wherein said rheologyagent is selected from the group consisting of: modified cellulosederivatives, cellulose ethers, starch derivatives, pectin derivatives,polyacylamides; and aqueous dispersions thereof.
 45. The method of claim40, wherein said rheology agent is selected from the group consistingof: hydroxypropylcellulose, hydroxyethylcellulose, other celluloseethers and carboxymethylcellulose.
 46. The method of claim 40, whereinsaid rheology agent comprises hydroxypropylcellulose.
 47. The method ofclaim 40, wherein said oxidizing agent is selected from the groupconsisting of: hydrogen peroxide (H₂O₂), ferric nitrate (Fe(NO₃)₃),potassium iodate (KIO₃), potassium permanganate (KMnO₄), nitric acid(HNO₃), ammonium chlorite (NH₄ClO₂), ammonium chlorate (NH₄ClO₃),ammonium iodate (NH₄BO₃), ammonium perborate (NH₄BO₃), ammoniumperchlorate (NH₄ClO₄), ammonium periodate (NH₄BO₃), ammonium persulfate((NH₄)₂S₂O₈), tetramethylammonium chlorite ((N(CH₃)₄)ClO₂),tetramethylammonium chlorate ((N(CH₃)₄)ClO₃), tetramethylammonium iodate((N(CH₃)₄)IO₃), tetramethylammonium perborate ((N(CH₃)₄)BO₃),tetramethylammonium perchlorate ((N(CH₃)₄)ClO₄), tetramethylammoniumperiodate ((N(CH₃)₄)IO₄), tetramethylammonium persulfate((N(CH₃)₄)S₂O₈), urea hydrogen peroxide ((CO(NH₂)₂)H₂O₂),4-methylmorpholine N-oxide (C₅H₁₁NO₂) and pyridine-N-oxide (C₅H₅NO). 48.The method of claim 40, wherein said oxidizing agent comprises hydrogenperoxide.
 49. The method of claim 40, wherein said chelating agent isselected from the group consisting of: phosphoric acid, glycine,alanine, citric acid, acetic acid, maleic acid, oxalic acid, malonicacid, succinic acid, nitrilotriacetic acid, iminodiacetic acid,ethylenediamine, and EDTA.
 50. The method of claim 40, wherein saidchelating agent comprises glycine.
 51. The method of claim 40, whereinsaid corrosion inhibitor is selected from the group consisting of:imidazole, aminotetrazole, benzotriazole, benzimidazole, oxalic acid,malonic acid, succinic acid, nitrilotriacetic acids, iminodiaceticacids, and derivatives and combinations thereof.
 52. The method of claim40, wherein said corrosion inhibitor comprises 5-aminotetrazole (ATA) or5-aminotetrazole monohydrate.
 53. The method of claim 40, wherein thecomposition has a pH that is between about 2 and
 11. 54. The method ofclaim 40, wherein said solvent is selected from the group consisting ofwater, organic solvent and combinations thereof.
 55. The method of claim40, wherein said solvent is selected from the group consisting of:water, methanol, ethanol, propanol, butanol, ethylene glycol, propyleneglycol, glycerin, and combinations thereof.
 56. The method of claim 40,wherein the rheology agent causes abrasive particles to becomeconstrained in a flow plane between a wafer substrate surface and apolishing pad.
 57. The method of claim 40, wherein shear rate is greaterat elevated wafer substrate topography than at via and line trenches.58. The method of claim 40, wherein the CMP composition is formulated asa two-part composition in which the first part comprises all componentsof the composition except the oxidizing agent, and the second partcomprises the oxidizing agent.
 59. The method of claim 40, wherein theremoval selectivities of copper and liner materials is altered byreducing the concentration of the oxidizing agent in situ.